Mancos Shale

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Mancos Shale Formation
Stratigraphic range: middle Albian to Campanian
Mancos Shale badlands in Capitol Reef NP.jpg
Mancos Shale badlands in Capitol Reef National Park, southern Utah.
Type Geologic formation
Underlies Mesaverde Formation
Overlies Dakota Group
Location
Region Arizona, Colorado, New Mexico, Utah, Wyoming
Country United States
Type section
Named for Mancos, Colorado
Mancos Shale and Mowry Shale oil and gas fields within the Uinta Basin and Piceance Basin
Stratigraphic column showing the relationship of the Mancos and Mowry shales

The Mancos Shale or Mancos Group is a Late Cretaceous (Upper Cretaceous) geologic formation of the Western United States.

The Mancos Shale was first described by Cross and Purington in 1899[1] and was named for exposures near the town of Mancos, Colorado.

Geology[edit]

It is dominated by mudrock that accumulated in offshore and marine environments of the Cretaceous North American Inland Sea. The Mancos was deposited during the Cenomanian (locally Albian) through Campanian ages, approximately from 95 Ma to 80 Ma.

Stratigraphically the Mancos Shale fills the interval between the Dakota Group and the Mesaverde Formation Group.[2]

The Mancos Shale rests conformably on the Dakota and in its upper part grades into and intertongues with the Mesaverde Group. The shale tongues typically have sharp basal contacts and gradational upper contacts.

The classification broadly correspondences with the Colorado Group classification of the Great Plains region; as such, various units of the Colorado Group are recognized within the Mancos.[3]

Occurrences[edit]

The Mancos occurs in the Basin and Range Province, the Colorado Plateau Province, and the San Juan Mountains Province.

Structural basins[edit]

It also occurs in the following structural basins:[4]

Subunits[edit]

The Mancos occurs with the following subunit names (listed alphabetically):[4] (bold: principle reference section at the type location)[6][7]

  • Anchor Mine Tongue (CO, UT),
  • Aspen Member (UT,WY),
  • Black Butte Tongue (WY),
  • Blue Gate Member (UT),
  • Fairport Member (CO)
  • Blue Hill Member (CO, NM),
  • Buck Tongue (CO,UT),
  • Bull Point Sandstone Member (UT),
  • Carlile Member (NM),
  • Clay Mesa Tongue (NM),
  • Cortez Member (CO)
  • Cooper Arroyo Sandstone Member (NM),
  • D-Cross Tongue (NM),
  • Devils Grave Sandstone [Member] (CO),
  • El Vado Sandstone Member (NM),
  • Emery Sandstone Member (UT),
  • Fairport Member (CO)
  • Ferron Sandstone Member (CO, UT),
  • Fort Hays Limestone Member (CO),
  • Frontier Formation (CO, UT),
  • Garley Canyon Sandstone Member (UT),
  • Graneros Member (CO, NM),
  • Greenhorn Member (NM),
  • Hartland Shale Beds (NM),
  • Hopi Sandy Member (AZ),
  • Horsehead Tongue (NM),
  • Hunt Creek Sandstone [Member] (CO),
  • Juana Lopez Member (CO, NM),
  • Loyd Sandstone Member (CO),
  • Masuk Member (UT) or Masuk Tongue (UT),
  • Meeker Sandstone Member (CO),
  • Montezuma Valley Member [Carlile] (CO)
  • Morapos Sandstone Member (CO),
  • Mowry Member (UT) or Mowry Shale (CO, UT),
  • Mulatto Tongue (NM),
  • Muley Canyon Sandstone Member (UT),
  • Niobrara Member (CO, NM),
  • Pescado Tongue (AZ, NM),
  • Rangely Tongue (CO, UT),
  • Rio Salado Tongue (NM),
  • Sanastee Sandstone Member (NM),
  • Satan Tongue (NM),
  • Semilla Sandstone Member (NM),
  • Smoky Hill Member (CO)
  • Tocito Sandstone Lentil (CO, NM),
  • Tununk Member (UT),
  • Whitewater Arroyo Tongue (NM),
  • Wildcat Canyon Sandstone Member (UT),
  • Wind Rock Tongue (AZ).

See also[edit]

References[edit]

  1. ^ Cross, W. and Purington, C. W. (1899) "Description of the Telluride quadrangle, Colorado" United States Geological Survey Atlas, Folio 57
  2. ^ Weimer, R. J. (1960) "Upper Cretaceous Stratigraphy, Rocky Mountain Area" American Association of Petroleum Geologists Bulletin 44: pp. 1-20
  3. ^ Charlse H. Rankin. "Stratigraphy of the Colorado Group, Upper Cretaceous, in Northern New Mexico" (PDF). New Mexico Bureau of Mines and Mineral Resources Bulletins. New Mexico School of Mines (20): 5. Retrieved 2018-08-13. ...that all divisions of the Colorado group (Mancos shale) as described in southern Colorado, except the Fort Hays lime-stone and the Apishapa shale, can be recognized in northern New Mexico. 
  4. ^ a b "Colorado River Basin Stratigraphy: Mancos Shale" United States Geological Survey
  5. ^ New Mexico Geological Association.edu: "SURFACE and SUBSURFACE STRATIGRAPHY of the BURRO CANYON FORMATION, DAKOTA SANDSTONE, and INTERTONGUED MANCOS SHALE of the CHAMA BASIN, NEW MEXICO"; 2005.
  6. ^ R. Mark Leckie, James I. Kirkland, and William P. Elder (1997). "Stratigraphic Framework and Correlation of a Principle Reference Section of the Mancos Shale (Upper Cretaceous), Mesa Verde, Colorado" (PDF). 48th Annual NMGS Fall Field Conference Guidebook. Mesozoic Geology and Paleontology of the Four Corners Area: 288. Retrieved 2018-08-04. 
  7. ^ Russell K. Lewis, Stratigraphy and depositional environments of the Late Cretaceous (Late Turonian) Codell sandstone and Juana Lopez members of the Carlile shale, southeast Colorado, 2013 - Mines Theses & Dissertations, retrieved 2018-08-14